/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.solr.cluster.placement;

/**
 * Metric-related attribute of a node or replica. It defines a short symbolic name of the metric,
 * the corresponding internal metric name and the desired format/unit conversion. Generic type
 * specifies the type of converted values of this attribute.
 */
public interface Metric<T> {

  /** Return the short-hand name that identifies this attribute. */
  String getName();

  /** Return the internal name of a Solr metric associated with this attribute. */
  String getInternalName();

  /**
   * Convert raw value. This may involve changing raw value type or units.
   *
   * @param value raw value
   * @return converted value
   */
  T convert(Object value);

  /**
   * Return the label key for Prometheus metrics filtering, if any.
   *
   * @return label key or null if no label filtering is needed
   */
  default String getLabelKey() {
    return null;
  }

  /**
   * Return the label value for Prometheus metrics filtering, if any.
   *
   * @return label value or null if no label filtering is needed
   */
  default String getLabelValue() {
    return null;
  }

  /**
   * Return true if this metric has label filtering.
   *
   * @return true if both label key and value are non-null
   */
  default boolean hasLabels() {
    return getLabelKey() != null && getLabelValue() != null;
  }
}
